Complete Phenotypic Expression of Hypohidrotic Ectodermal Dysplasia in a Female Patient.

Sir,

Hypohidrotic ectodermal dysplasia (HED) is a genodermatosis characterized by classic triad of hypotrichosis, anodontia/oligodontia, and hypohidrosis/anhidrosis. HED is mostly inherited in X-linked recessive manner with complete expression of classical clinical features in males. Females have few to no symptoms. Very few cases of females with classic features of HED with autosomal inheritance has been reported.[12]

A 23-year-old female presented in Dermatology outpatient department of our hospital with the chief complaints of small papular eruption on cheeks and forehead for last 7 years along with impaired sweating and heat intolerance since birth.

On examination, she had sebaceous hyperplasia over forehead and cheeks, sparse scalp hair, no eyebrows over medial two-third, absent eyelashes, prominent supraorbital ridges, depressed nasal bridge, and dry and prominent lips [Figure 1]. She had sparse axillary hair but normal pubic hair. Her skin surface was smooth and dry. Examination of palms and soles revealed fissured soles and absent dermatoglyphics on finger tips.

Figure 1

Patient having facies with depressed nasal bridge, prominent and arched supraorbital ridges, prominent lips, and scant to absent eyebrows

On oral examination, there was oligodontia [Figure 2]. Examination of external genitalia, breast, and nails revealed no abnormality. Other systemic examinations (including CNS) revealed no abnormality.

Figure 2

Oligodontia with only five erupted permanent teeth in both gums

She was a graduate with normal intelligence. There was no history of febrile seizure in her childhood. Her family history revealed that she was born out of consanguineous marriage to normal parents and has an elder brother who is normal. There was no history of similar illness in her family.

Starch-Iodide testing revealed her to be hypohidrotic [Figure 3].

Figure 3

Starch-Iodide test demonstrating small and very few dark blue dots suggesting hypohidrosis

Genetic testing could not be done.

A diagnosis of HED was made.

She was advised electrocautery for sebaceous hyperplasia; 2% minoxidil was advised for scalp application and was referred to Dental Department for oligodontia to consider orthodontics/reconstruction.

Ectodermal dysplasias are characterized by congenital defects in two or more major ectodermal structures, one of which at least involves the sweat glands, hair, teeth, or nails. Hypohidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome) is the most common of the ectodermal dysplasias. This disorder is characterized by sparse or absent eccrine glands, hypotrichosis, and oligodontia.

Hypohidrotic ectodermal dysplasia is caused by mutation of genes that are involved in the ectodysplasin signal transduction pathway. This cascade activates within epithelial cells at a critical time during embryogenesis. It leads to expression of target genes that are involved in the morphogenesis of eccrine sweat glands, hair follicles, and teeth. EDA gene encodes the ectodysplasin ligand, which initiates signaling through ectodysplasin pathway. X-linked recessive (XLR) form of HED (75%–95% of HED cases) is due to mutation in EDA gene.[3]

Mutation in the EDAR gene can be identified in ~25% of HED patients, who do not have an EDA defect.[4] EDAR is a transmembrane protein in the TNF receptor family, and its intracellular portion contains a death domain, which interacts with an adaptor protein, EDARADD. Dominant-negative EDAR mutations produce an autosomal dominant (AD) form of HED, whereas other EDAR mutations result in an autosomal recessive (AR) form of HED. Mutations in the EDARADD gene may also underlie both AD and AR forms of HED.[5]

There are no clinical features to differentiate autosomal inherited HED from XLR HED. Only distinguishing feature is that in autosomal HED, both sexes are affected. But in XLR HED, only males are affected with females as silent carrier.

Previously, few female patients with classic features of HED and autosomal inheritance have been reported.[12]

Since there is almost full expression in this female patient, probably it is of AD inheritance in this case.

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